Apparatus for removing photoresist film

ABSTRACT

An apparatus for removing a photoresist film includes a substrate cassette for fixing a substrate having a surface covered with a photoresist film, an ozone feed tube for supplying ozone, a liquid feed tube for supplying a liquid photoresist film removing solution, and a processing tank for recovering and processing at least one of ozone and the liquid photoresist film removing solution, wherein the liquid photoresist film removing solution is supplied through the liquid feed tube as a liquid or mist, at least one of ozone and the photoresist film removing solution being continuously supplied.

This disclosure is a division of U.S. patent application Ser. No.09/614,258 filed Jul. 12, 2000, now U.S. Pat. No. 6,517,999, which is acontinuation application of PCT international application No.PCT/JP99/06323, which has an international filing date of Nov. 12, 1999,and which designated the United States, the entire contents of which areincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method of removing a film containingan organic composition and, more particularly, to a method of removing aphotoresist film containing an organic polymer compound used in aphotolithographic process for producing a semiconductor device and thelike, and to an apparatus used in the method.

DESCRIPTION OF THE RELATED ART

A photoresist material is generally used in a photolithographic processfor forming a fine pattern and/or in a subsequent etching step forforming an electrode pattern in course of manufacturing a semiconductordevice, such as an integrated circuit, a transistor, a liquid crystaldevice, a diode and the like.

For example, when a silicon oxide layer is formed in a desired patternon a semiconductor substrate such as a silicon substrate (referred to asa silicon wafer), a silicon oxide layer is first deposited on thesurface of the substrate and cleaned before a photoresist materialsuited for forming the desired pattern is applied to the silicon oxidelayer to form a photoresist film. Then, a photo mask having a patterncorresponding to the desired pattern is placed on the photoresist film,exposed to light and then developed. Thereby, a photoresist film havingthe desired pattern, referred to a photoresist pattern, is obtained. Inthe subsequent etching step, the silicon oxide layer is removedaccording to the resulting photoresist pattern. Finally, after theremoval of the remaining photoresist film and the cleaning of thesurface of the substrate, the silicon oxide layer is remained on thesubstrate in the desired pattern.

In the etching step, an art-known method of removing a part of thephotoresist film unnecessary for the formation of the desired patternincludes, for example, [1] a method using an oxygen gas plasma and [2] amethod using various oxidizing agents.

In the method using an oxygen gas plasma [1], oxygen gas is introducedin the photoresist film under vacuum and a high voltage generates anoxygen gas plasma. Then, the photoresist film is decomposed and removedby reacting with the oxygen gas plasma. However, there had been someproblems in this method [1], including the requirement of an expensiveapparatus for generating the oxygen gas plasma, a potential of damagingthe substrate containing an electrical element due to the presence ofcharge carriers in the plasma, and the like.

Alternatively, as an example of the method [2] using various oxidizingagents to decompose and remove the photoresist film, for example, amethod using hot concentrated sulfuric acid or a mixture of hotconcentrated sulfuric acid and hydrogen peroxide as the oxidizing agentis known.

When using hot concentrated sulfuric acid, however, there is adisadvantage, such as an extremely high risk of heating strong sulfuricacid to 150° C.

On the other hand, when using the mixture of hot concentrated sulfuricacid and hydrogen peroxide, a substance having an oxidizing anddecomposing action is released according to the following scheme. In thescheme, on adding hydrogen peroxide to hot concentrated sulfuric acidheated to about 140°C., peroxosulfuric acid (H₂SO₅; generally referredto as Caro's acid) and oxygen atom (O) are generated as follows:

H₂SO₄+H₂O₂⇄H₂SO₅+H₂O  (1)

H₂O₂→O+H₂O  (2)

The organic photoresist film may be oxidized by the strong acidity ofboth peroxosulfuric acid and oxygen atoms and converted to an inorganicsubstance. The inorganic substance is decomposed by reacting with hotconcentrated sulfuric acid and then removed from the surface of thesubstrate.

However, as shown in the above schemes (1) and (2), this method [2] hasa problem that, since a sulfuric medium is diluted with water producedupon addition of hydrogen peroxide to hot concentrated sulfuric acid,the concentration of hot concentrated sulfuric acid after mixing isdecreased with time. The method [2] also has disadvantages, includingthe extremely high risk as described for the method [1], i.e., the useof strong sulfuric acid at an elevated temperature, and the heatgenerated when mixing hot concentrated sulfuric acid with hydrogenperoxide, and the necessity of an expensive exhaust system generatingstrong ventilation in order to operate the method in a clean room, andthe like.

As another oxidizing agent used to decompose the photoresist film otherthan hot concentrated sulfuric acid, there has been developed awater-immiscible solution for exclusively removing a photoresist film,such as, for example, a solution #106 consisting of 30% by volume ofdimethylsulfoxide and 70% by volume of monoethanolamine. However, suchoxidizing agent has problems, including its lower oxidation power thanhot concentrated sulfuric acid and a mixture of hot concentratedsulfuric acid and hydrogen peroxide, and the difficulty of treating thefoul solution which is immiscible with water.

In order to overcome the problems of the above methods [1] and [2], amethod of removing a photoresist film using a mixture of ozone with hotsulfuric acid as the oxidizing agent has been proposed (Japanese PatentKokai Publication No. Sho 57-180132). This publication discloses amethod to decompose and remove the organic substance (i.e. thephotoresist film) or the inorganic substance deposited on the substrateor the insulating layer by bubbling an ozone-containing gas in hotsulfuric acid. It also describes a washing apparatus used in the method(the cross sectional view of the apparatus is illustrated in FIG. 8).

The washing apparatus shown in FIG. 8 includes a quartz container 6″filled with hot concentrated sulfuric acid 5′ heated at approximately110 ° C., which is laid on a heater 11 and a quartz tube 120 havingplural outlets 3′. A raw gas (generally, oxygen) supplied through agas-introducing tube 111 provided outside the quartz container 6″ isconverted to an ozonized gas in an ozone generator 1. The ozonized gasis then injected through the quartz tube 120 into hot concentratedsulfuric acid 5′ in the quartz container 6 to react with sulfuric acid,and thereby, peroxosulfuric acid and an oxygen atom are produced. Byoxidizing the photoresist film with the strong acidity of bothperoxosulfuric acid and oxygen, the photoresist film on the surface ofthe substrate 8 (held with a substrate cassette 9), which is immersed inhot concentrated sulfuric acid, is removed.

In the method described in this publication, the concentration of thesulfuric acid does not change since water is not generated during thedecomposition of the photoresist film, and, therefore, frequency ofchanging the sulfuric acid may be decreased. The method, however, had aproblem that the cost for raw materials is too high because a largeamount of the sulfuric acid is needed to operate. Additionally, themethod and apparatus disclosed in the publication also have a high riskon working because of the use of strong sulfuric acid at an increasedtemperature in the same way as the conventional method, and also needsextremely strong ventilation since the oxidizing agent is vaporized bybubbling of the ozonized gas.

Accordingly, an object of the present invention is to provide a methodof removing a photoresist film at an increased rate, which decreasesboth usage of the raw materials and the cost for the exhaust system andis also environment-friendly, and to further provide an apparatus usedin the method, in order to overcome the above problems with theart-known method for removing the photoresist film and with theconventional apparatus used therefor.

Definition of the Technical Terms

As used herein, an “ozonized gas” means a gas mixture containing oxygenand a given amount of ozone. Hereinafter, a “sealed system” isthermodynamically classified into an open system, but it means one inwhich any of a gas and a solution are introduced therein and a gas or avapour generated in removing a photoresist film according to the presentinvention, and the like, are not released or spattered outside of thesystem.

SUMMARY OF THE INVENTION

According to the first aspect of the present invention, there isprovided a method of removing a photoresist film provided on a surfaceof a substrate, comprising steps of in a sealed system, disposing thesubstrate surface having the photoresist film to contact with aphotoresist film removing solution, making ozone exist in gas phaseand/or solution phase in the vicinity of the liquid surface of thephotoresist film removing solution, and changing a relative positionbetween the surface of the substrate and the liquid surface of thesolution to decompose or remove the photoresist film from thesubstarate, characterized in that the relative position is changedcontinuously or intermittently within a range between a position where abottom edge of the substrate is present above the liquid surface of thesolution, and another position where a top edge of the substrate ispresent below the liquid surface of the solution.

The photoresist film removing solution used in the present invention maybe a solution which is able to dissolve a desired quantity of ozone, andmay be selected from a group consisting of pure water, an acid andalkaline aqueous solutions and an organic solvent. According to themethod of the present invention, ozone and the photoresist film removingsolution may be simultaneously or separately supplied into a sealedsystem. Alternatively, ozone and the photoresist film removing solutionmay also be supplied simultaneously by incorporating ozone into thephotoresist film removing solution.

In the method of the present invention, the relative position betweenthe surface of the substrate and the liquid surface of the photoresistfilm removing solution can be controlled by the way of:

(1) moving the substrate itself; or

(2) changing a level of the liquid surface of the photoresist filmremoving solution.

The moving and changing may be continuously or intermittently conducted.

According to the method of the present invention, the photoresist filmremoving solution may be used in a mixed phase prepared by incorporatinga given amount of ozone therein. It may be also possible to applyultrasonic vibration into the sealed system.

Another method of the present invention includes a step of continuouslyor intermittently supplying the surface of the substrate having thephotoresist film thereon with an ozonized gas and the photoresist filmremoving solution in a form of mist. In this method, ozone and thephotoresist film removing solution may be simultaneously supplied byusing the photoresist film removing solution which incorporates ozonetherein.

According to the method of the present invention, the photoresist filmremoving solution which has been used in the system may be recovered andconditioned for reuse.

According to the second aspect of the present invention, there isprovided an apparatus for removing a photoresist film from a substrateused in a method of removing the photoresist film provided on a surfaceof the substrate, comprising steps of in a sealed system, disposing thesubstrate surface having the photoresist film to contact with aphotoresist film removing solution, making ozone exist in gas phaseand/or solution phase in the vicinity of the liquid surface of thephotoresist film removing solution, and changing a relative positionbetween the surface of the substrate and the liquid surface of thesolution to decompose or remove the photoresist film from thesubstarate, the relative position is changed continuously orintermittently within a range between a position where a bottom edge ofthe substrate is present above the liquid surface of the solution, andanother position where a top edge of the substrate is present below theliquid surface of the solution, wherein the apparatus comprising areaction vessel for charging a photoresist film removing solution, anozone feed tube having an outlet for injecting ozone into thephotoresist film removing solution, a substrate cassette for disposingand fixing the substrate to contact with a liquid surface of thephotoresist film removing solution, a cassette carrier unit for movingthe substrate cassette and a processing tank for recovering andprocessing ozone and/or the photoresist film removing solution.According to the apparatus of the present invention, ozone and thephotoresist film removing solution can be simultaneously or separatelysupplied into the reaction vessel.

In the apparatus of the present invention, the relative position betweenthe surface of the substrate and the liquid surface of the solution maybe optionally changed within the range from a position where a bottomedge of the substrate is present above the liquid surface of thesolution and another position where a top edge of the substrate ispresent below the liquid surface of the solution, by continuously orintermittently moving the cassette carrier unit, or by continuously orintermittently controlling the supplement of the photoresist filmremoving solution into the reaction vessel and the discharge thereoffrom the reaction vessel.

In the apparatus of the present invention, in case of the supply anddischarge of the photoresist film removing solution supply, the reactionvessel may have an automatically operated valve for changing a level ofthe liquid surface of the photoresist film removing solution.

The apparatus of the present invention further comprises an ultrasoundgenerator. In this case, the removing solution used in the apparatus ispreferably supplied in a mixed phase containing ozone, wherein thesolution is free from bubbles.

The present invention also provided an apparatus for removing aphotoresist film, comprising a substrate cassette for fixing a substratehaving a photoresist film on a surface of the substrate, an ozone feedtube, a liquid feed tube for supplying the photoresist film removingsolution and a processing tank for recovering and processing ozoneand/or the photoresist film removing solution. The photoresist filmremoving solution supplied through the liquid feed tube may be in a formof liquid or mist, while ozone and the photoresist film removingsolution may be continuously or intermittently supplied. The reactionvessel has a means for reusing or discharging the photoresist filmremoving solution and/or ozone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a cross-sectional view illustrating anapparatus for removing a photoresist film according to the presentinvention.

FIG. 2 conceptually shows a diagram illustrating the process of removinga photoresist film in a method of removing a photoresist film of thepresent invention.

FIGS. 3(a) and 3(b) conceptually show a diagram illustrating therelative position between the surface of the substrate and the liquidsurface of the photoresist film removing solution versus a period oftime taken to remove a photoresist film in a method of removing aphotoresist film according to the present invention.

FIG. 4 schematically shows a cross-sectional view of an apparatus forremoving photoresist film according to the present invention.

FIG. 5 schematically shows a cross-sectional view of an apparatus forremoving a photoresist film according to the present invention.

FIG. 6 schematically shows a cross-sectional view of an apparatus forremoving a photoresist film according to the present invention.

FIG. 7 schematically shows a cross-sectional view of an apparatus forremoving a photoresist film according to the present invention.

FIG. 8 schematically shows a cross-sectional view of an apparatus forremoving a photoresist film described in the background art.

PREFERRED EMBODIMENTS OF THE INVENTION

A method of the present invention and an apparatus used in the methodwill be described in detail below by way of preferred embodiments. Itshould be noted, however, that the present invention is not limited tothese embodiments, and various changes and modifications that areapparent for those skilled in the art are within the scope of thepresent invention.

Embodiment 1

The embodiment 1 relates to a method of removing a photoresist filmusing an apparatus for removing a photoresist film (A1, FIG. 1) as thesecond aspect of the invention.

In the present application, the photoresist film to be removed mayinclude either a film formed from a photoresist material containing anorganic polymer compound, which the photoresist material is used in anyprocesses of manufacturing semiconductor devices, a film decomposed byheating, a film of which the surface is modified by heating or heavydoping, or a film having a surface on which an inorganic substance isdeposited in an etching process.

The substrate of which the surface has the photoresist film may includesilicon wafer, a glass substrate for a liquid crystal display device, aglass-reinforced epoxy substrate used for producing a printed-circuit,and the like, but is not particularly limited thereto as long as it maybe any one commonly used in the manufacture of semiconductor devices.

Apparatus

An apparatus (A1) of the present invention shown in FIG. 1 is operatedroughly as follows. First, a raw gas mainly containing oxygen issupplied through an ozone gas feed tube 111 to ozonize at least 5 mole%, preferably from 5 to 100 mole % of the raw gas on an ozone generator1. In this specification, the gas containing ozone will be called the“ozonized gas” for simplicity, hereinafter.

A content of ozone in the ozonized gas may change depending on the sizeof the substrate to be processed and the type of the photoresistmaterial used. An amount of the gas containing oxygen which is suppliedto the ozone generator 1 may change depending on the necessary contentof ozone in the ozonized gas.

The resulting ozonized gas is mixed in an ejector 2 with a photoresistremoving solution supplied through a pump 4, to prepare a photoresistremoving solution 5 containing the ozonized gas. This solution 5 isintroduced through a liquid feed tube 114 into a reaction vessel 6placed in a sealed container 7.

The apparatus (A1) of the present invention has a check valve 113installed upstream the ejector 2 in order to prevent the moisture fromentering to the ozone generator 1 that would significantly reduce theamount of ozone generated. More preferably, the amount of gas suppliedto the ozone generator 1 may be controlled by equipping a detector fordetecting the amount of gas to close the check valve 113 when the rawgas is not supplied.

The photoresist film removing solution that can be used in the presentinvention may be selected from a group consisting of pure water; an acidaqueous solution, such as sulfuric acid, hydrochloric acid, nitric acid,acetic acid and hydrogen peroxide; an alkaline aqueous solution, such asammonium hydroxide; an organic solvent, such as ketones includingacetone and the like, and alcohols including isopropanol and the like;and a mixture thereof. Although pure water may be most preferably usedin view of waste water treating and the like, any of the above solventsother than pure water or a mixture thereof may be desirably used when itis intended to increase a rate of removing the photoresist film, or toremove the modified film by heavy ion doping or contaminants depositedon the surface of the substrate.

An amount of ozone in the photoresist removing solution containing theozonized gas used in the apparatus (A1) of the present invention is inthe state of saturation, and may preferably be in a range from 10 to 200ppm at 20° C. The amount may be varied by controlling the content ofozone contained in the ozonized gas.

An excess amount of the photoresist removing solution containing theozonized gas 5 is overflown (arrow 51 in FIG. 1) from the reactionvessel 6, recovered in the sealed container 7 and then recycled througha filter 41 to reuse.

Unnecessary ozonized gas after processing is carried through an ozoneoutlet tube 131 to a waste ozone processor 13 to reduce to oxygen, andthen is discharged to the atmosphere.

Accordingly, since removing the photoresist film is conducted in thesealed container, the apparatus of the present invention may not releaseharmful gas to the atmosphere while there is no necessary for anelaborate ventilation facility. The apparatus of the present inventionmay also reduce the amount of starting materials since the solution usedcan be recycled to reuse after the operation.

When the apparatus (A1) of the present invention is used to process asubstrate 8 having the photoresist film on the surface thereof, thesubstrate 8 is fixed in a substrate cassette 9 in a predetermineddirection. In the substrate cassette 9, a fixing means (such as agroove) may be provided so that a desired number of substrates to beprocessed at the same time can be held in parallel to each other, eachsubstrate being apart from at a proper interval. The substrate cassette9 can be moved up and down in the sealed container 7 with moving acassette carrier unit 10 to which the substrate cassette 9 is fixed.

Moving the substrate cassette 9 up and down is most preferably conductedat the angle to arrange the surface of the substrate substantiallynormal to the liquid surface of the photoresist removing solution.However, in the present invention, the angle is not particularly limitedthereto, as long as the surface of the substrate may be effectively incontact with the liquid surface of the photoresist removing solution.

In FIG. 1, the substrate 8, the substrate cassette 9 and the cassettecarrier unit 10, all of which are drawn with solid lines, depict thestate where the substrate is brought to the top position (i.e. aposition where a bottom edge of the substrate is present above theliquid surface) by the cassette carrier unit 10, and those drawn withdashed lines depict the state where the substrate is brought to thebottom position (i.e. a position where a top edge of the substrate ispresent below the liquid surface). According to the present invention,the substrate to be processed is subjected to at least one pass of amovement, each pass being consisting of the motion from the top positionto the original top position through the bottom position. The substratemay move either continuously or discontinuously (that isintermittently).

Process of Removing Photoresist Film

The process of removing a photoresist film according to the method ofthe present invention, including the vertical movement of the substrate,will be described in detail with reference to a conceptual diagram ofFIG. 2.

In FIG. 2, the substrate 8, having a photoresist film 81 on a surfacethereof, is immersed up to a half surface from its bottom end in thephotoresist film removing solution containing the ozonized gas 5. Whenpure water was used as the photoresist film removing solution, and theozonized gas was incorporated into pure water to obtain a mixturecontaining 50 ppm of ozone at 20° C., a rate to remove the photoresistfilm in the mixture by the oxidization and the decomposition was withina range from about 0.04 to about 0.08 μm/min.

In the photoresist film removing solution containing the ozonized gas 5,the photoresist film 81 on the surface of the substrate 8 is coated bythe solution 5, resulting in a reduced diffusion rate of ozone. As aresult, the photoresist film 81 coated by the solution 5 is decomposedto some extent to make the molecular of the organic compositionformulated in the film lower, but then, the oxidation does noteffectively proceed. On the other hand, in a region near a gas-liquidinterface 82 between the liquid surface of the photoresist film removingsolution containing the ozonized gas 5 and the atmosphere (i.e. theregion within about 1 cm above the liquid surface), there exists ozonein a high concentration, and it can be supplied to the photoresist film81 coated by the film of the solution 5, and thereby, the photoresistfilm can make contact with far more ozone in this region than in thesolution. Near the gas-liquid interface 82, the photoresist film 8 canbe oxidized and decomposed at a rate several times faster than the ratedescribed above.

Further, bursting bubbles containing ozone (number 52 in FIG. 2) in airproduce the ozone-incorporating pure water surrounding the bubblesdeposited on the substrate. The present inventors have found that whenthe ozone-incorporating pure water, i.e., the photoresist removingsolution containing the ozonized gas, deposited on the substrate flowsdown by gravity, it also has an action of washing down the lowermolecular weight organic composition formulated in the film (namely,cleaning action).

In the apparatus (A1) of this embodiment where the substrate 8 itself ismoved, when moving the substrate 8 upward from within the photoresistfilm removing solution containing the ozonized gas 5, the substratemoves at a constant speed (preferably from 1 to 100 cm/min.) from theposition of H min to the position of H mix (region I), as shown in FIG.3(a). This makes the photoresist film removing action which brings aboutnear the gas-liquid interface effective over the whole of the substrate.

The movement may be continuously or intermittently conducted. That is,the substrate may move continuously at a constant speed, or it may moveeach given relative position between the surface of the substrate andthe liquid surface of the solution at certain time intervals (preferablyeach 1 to 10 cm every 0.5 to 10 minutes).

When in the apparatus (A1), the substrate 8 moves downward to immerse inthe photoresist film removing solution containing the ozonized gas 5, itmay move faster than the upward movement (for example at 10 cm/min orfaster, most preferably at between 10 and 1000 cm/min) (region II inFIG. 3(a)). When the substrate 8 is immersed in the solution 5 at afaster speed, it may cause a friction force between the photoresist film81 and the liquid surface of the solution 5, and thereby, it may peeloff or dissolve even the remaining photoresist film having a relativelylarge molecular weight in the solution.

Then, the remaining photoresist film having the relatively largemolecular weight which is present or dissolved in the photoresist filmremoving solution containing the ozonized gas 5 may be oxidized ordecomposed in the solution, or it may be recovered in the sealedcontainer 7 and then collected on the filter 41. When a heating unit isinstalled on the filter 41, the remaining photoresist film can be moreefficiently decomposed, and thereby, the frequency of changing thephotoresist film removing solution containing the ozonized gas 5 may bereduced.

In this embodiment, the substrate may move up and down at least one passas described hereinbefore.

At last of the process according to the present invention, when thesubstrate lifts quickly from within the photoresist film removingsolution containing the ozonized gas 5, the photoresist film can readilypeel off, and thereby, the subsequent step of cleaning of the substratemay be conducted more efficiently (region III in FIG. 3(a)).

According to the method and the apparatus of the present invention, thesubstrate may be moved discontinously (i.e. intermittently) as shown inFIG. 3(b). For instance, after holding the substrate 8 in the ozonizedgas for 0.5 to 2 minutes, the substrate 8 may be immersed in thephotoresist film-removing solution containing the ozonized gas 5 for 10seconds to one minute. The movement of the substrate from air into thesolution 5 may be particularly effectively conducted after the solutionremaining on the surface of the substrate is dried.

According to the present invention, when the process may include a stepof rapidly moving the substrate vertically during the movement thesubstrate 8 up and down, it may make the photoresist film easier to peeloff, and therefore, the rate to remove the film may be increased.

While the rate to remove the photoresist film may change depending onthe photoresist material used for the process and on the method ofprocessing the film in this embodiment, the rate to remove the film isbetween about 0.1 and 5 μm/min as measured. The rate shows that themethod of the present invention may improve the process of removing thefilm several times more effectively compared with the art-known method.

Embodiment 2

The above embodiment 1 illustrates the method and the apparatus ofmoving the substrate itself in order to change the relative position ofthe surface of the substrate and the liquid surface of the solution. Thepresent invention, however, also provides another method and apparatuswhich can change the liquid surface of the photoresist film removingsolution to control the relative position. FIG. 4 shows an apparatuswhich is able to change the liquid surface of the solution to controlthe relative position.

The apparatus (A2) shown in FIG. 4 has a constitution typically similarto that of the apparatus (A1) shown in FIG. 1 (that is, the raw gas is aoxygen-containing gas, and any of the photoresist film removing solutiondescribed in embodiment 1 may be used). In the apparatus (A2) ofembodiment 2, however, it is not essential to move the substrate 8vertically using the cassette carrier unit 10 in the sealed container 7.An automatically operated valve 61 is equipped with the reaction vessel6 in the sealed container 7 to control the liquid surface of thephotoresist film removing solution containing the ozonized gas 5. Theautomatically operated valve 61 may be installed in any walls or in thebottom of the reaction vessel 6.

The rate to change the liquid surface of the photoresist film removingsolution containing the ozonized gas 5 using the automatically operatedvalve 61 may be similar to the rate to move the substrate 8 by means ofthe cassette carrier unit 10 described in above embodiment 1. Ifnecessary, the liquid surface may be changed either continuously orintermittently.

The rate to change the liquid surface of the photoresist film removingsolution containing the ozonized gas 5 is preferably controlled bymaking reference to the above description related to FIGS. 3(a) and3(b).

Embodiment 3

The present invention also provides a different method and apparatusother than those described above embodiments 1 and 2, further includingan ultrasound generating means in the apparatus, and applying ultrasonicvibration to the photoresist film removing solution containing theozonized gas and the substrate using the ultrasound generating means, inorder to improve the efficiency of the process capacity.

FIG. 5 illustrates an example of an apparatus of removing a photoresistfilm (A3) used in this embodiment 3, wherein most of the apparatus maybe the same as that described in this embodiment 1, with the exceptionof an element and a function specifically described).

The ultrasound generating means 71 used in the apparatus (A3) of theembodiment 3 may be one that is well known in the prior art. Theultrasound generating means 71 is laid adjacent to the bottom of thesealed container 7 in FIG. 5, but is not limited thereto. As long as theultrasonic vibration can be effectively applied to both the photoresistfilm removing solution containing the ozonized gas 5 and the substrate8, the ultrasound generating means 71 may be installed, for example, onthe bottom of the reaction vessel.

In FIG. 5, first, the raw gas (i.e. an oxygen-containing gas; notindicated in FIG. 5) is sent to the ozone generator 1 from the ozone gasfeed tube 111 through a blower 116. The gas, a part of which has beenozonized, is supplied to a membrane type dissolution module 21 and ismixed with the solution supplied by the pump 4 to obtain the photoresistfilm removing solution containing the ozonized gas 5. This solution issupplied through the liquid feeder tube 114 and injected from the outlet3 into the reaction vessel 6 in the sealed container 7. Excess gas thathas not been dissolved in the solution 5 is circulated to pass throughthe blower 116 and the ozone generator 1 to send to the membrane typedissolution module 21 again. When the circulating gas contains somemoisture, the efficiency of the generation of ozone on the ozonegenerator 1 may decrease with time. In this embodiment 3, since acooling dehumidifier 115 is installed between the blower 116 and theozone generator 1 to remove the moisture, the efficiency of thegeneration of ozone on the ozone generator 1 may be prevent fromdecreasing with time.

The substrate 8 may be completely immersed in the reaction vessel 6filled with the photoresist film removing solution containing theozonized gas 5. When the ultrasound generating means 71 works, theultrasonic vibration is reached to both the photoresist film removingsolution containing the ozonized gas 5 and the substrate 8. Thevibration breaks the coating made of the solution 5 covering thephotoresist film on the substrate 8. Thereby, the frequency with whichthe photoresist film may contact with the photoresist film removingsolution containing the ozonized gas 5 may be increased, and then, therate to remove the photoresist film may significantly increase.

Embodiment 4

The embodiment 4 describes a method of supplying ozone and thephotoresist film removing solution separately, and further describes anapparatus (A4) used for the method.

FIG. 6 illustrates an apparatus of removing a photoresist film (A4),equipped with in the sealed container 7, the reaction vessel 6 which ischarged with the photoresist film removing solution 31, the cassettecarrier unit 10 for vertically moving the substrate 8, and feeder tubes112 and 117 for separately supplying the photoresist film removingsolution 31 and the ozonized gas 110 from the outside into the sealedcontainer. Since the ozonized gas 110 is not mixed with the photoresistfilm removing solution 31, but is supplied directly from the ozonegenerator 1 through the ozone gas feed tube 112 into sealed container 7,ozone can be supplied in high concentration. In this apparatus (A4), itis not necessary to circulate the photoresist film removing solution 31so that the desired amount of the photoresist film removing solution 31is supplied through the liquid feed tube 117 when necessary. Most of theapparatus may be the same as that described in this embodiment 1, withthe exception of an element and a function specifically described.

In this embodiment 4, first, the substrate 8 is completely immersed inthe solution 31. Then, the substrate 8 is lifted completely out of thesolution 31 to contact with the ozonized gas 110 supplied apart from thesolution 31. This causes the formation of a coating of the solution 31on the surface of the photoresist film, and thereby, the ozonized gasmay readily penetrate into the photoresist film, and the rate to removethe film may be further increased.

An example of the photoresist film removing solution 31 used in theembodiment 4 may be any of those described in the above embodiment 1,and more preferably includes isopropyl alcohol in view of its easierformation of the coating of the solution film on the surface of thephotoresist film easier and its ready evaporation.

In the embodiment 4, the photoresist film removing solution may beheated using a heating means (11 in FIG. 6) conventionally employed inthe art in order to increase the rate to decompose the photoresist filmand to accelerate the evaporation of the coating of the solution film onthe surface of the substrate. By installing the heating means, while theremaining photoresist film on the surface of the substrate, having thedecreased molecular weight by the decomposition or the peeling off, canbe more efficiently decomposed, the frequency of changing the solutioncan be also reduced. In this case, the photoresist film removingsolution 31 may be heated to any temperature up to 100° C.

Embodiment 5

This embodiment 5 is characterized in that the ozonized gas and thephotoresist film removing solution in a form of mist are suppliedseparately, and either continuously or intermittently.

In this embodiment 5, an apparatus for removing a photoresist film (A5)exemplified in FIG. 7 can be used. The apparatus (A5) includes the ozonegas feed tube 112 for supplying the ozonized gas 110 to the sealedcontainer 7, the liquid feed tube 117 for supplying the photoresist filmremoving solution in the form of mist (for example, number 31 in FIG. 7indicates the photoresist film removing solution in the form of mist), aliquid injection nozzle 300 for supplying a washing solution in a formof mist (for example, number 31′ in FIG. 7 indicates the washingsolution in the form of mist) and processing devices 151 and 13 forrecovering and processing the excess ozonized gas 110, and/or thephotoresist film removing solution 31 and the washing solution 31′ whichhave been used. The substrate 8 is fixed using a proper means (notshown) in the sealed container 7.

In the process of removing the photoresist film using the apparatus(A5), first, the substrate 8 is fixed in the sealed container 7. Then,the photoresist film removing solution 31 is sprayed through ahumidifier 301 from the liquid feed tube 117. The photoresist filmremoving solution 31 used in this embodiment 5 may be the same one asthat described in the above embodiment 1. The solution may also besprayed continuously or intermittently. An amount of the solution tospray may be changed depending on the size of the substrate to beprocessed and the thickness of the photoresist film.

At the same time of, before or after the spray of the solution, theozonized gas 110 generated on the zone generator 1 is supplied throughthe ozone gas feed tube 112 to the sealed container 7.

The photoresist film removing solution 31 in the form of mist, which hasbeen supplied, provides a thin coating on the photoresist film on thesurface of the substrate. The photoresist film is subsequently oxidizedand decomposed, or peeled off, by the action with ozone existing in thesealed container 7, and then, a photoresist component having lowmolecular weight that has been decomposed or peeled off, which isremained in the photoresist film, is dissolved in the coating.

When the oxidized and decomposed component dissolves in the coating ofthe solution, the ozonized gas is consumed to decompose the componentdissolved in the coating so that it may be sufficiently reached to thephotoresist film on the substrate. Therefore, the surface of thesubstrate may be preferably washed by spraying a solution having thesame formulation as the photoresist film removing solution 31 or purewater as a washing solution from the liquid injection nozzles 300 to thesubstrate 8 every certain time intervals. Spraying may be preferablyintermittently conducted at the same time intervals as those of movingthe substrate 8 (for example, sprayed each for 10 seconds to one minuteevery 0.5 to 2 minutes).

Then, faster removal of the photoresist film can be accomplished byrepeating several times a pass of the process, consisting of sprayingthe solution, oxidizing and decomposing the photoresist film on thesubstrate by contacting with ozone, and washing the substrate.

An excess of the ozonized gas 110, and the photoresist film removingsolution 31 and washing solution 31′ which have been used in the processmay be discarded or reused after the recovery and/or the process thereofin a processing tank 151 or a waste-ozone processor 13. In order toimprove the efficiency of the process, a heating means 11, such as aknown heater, may be equipped with the processing tank 151.

All of the methods and the apparatuses according to these embodiments 1to 5 are accomplished by considering further the disposal of the wastesolution and the exhaust gas, and therefore, the extremely fast removalof the photoresist film can be also performed.

Effects of the Invention

According to the method of the present invention, frequency of thecontact of ozone with the photoresist film removing solution may beincreased by changing the relative position between the surface of thesubstrate to be processed and the liquid surface of the solution, andthereby, the rate to decompose and remove the photoresist film may beimproved.

The photoresist film removing solution used in the invention may be anyof known solvents selected from a group consisting of pure water, anaqueous acid and alkaline solutions, and organic solvents, as long as itcan dissolve ozone. In the present invention, ozone and the photoresistfilm removing solution can be supplied simultaneously by incorporatingozone into the photoresist film removing solution, and thereby, the rateto decompose and remove the photoresist film can be further accelerated.The cost of starting material can be readily controlled since each ofozone and the photoresist film removing solution can be also suppliedseparately.

According to the present invention, the change of the relative positioncan be performed by moving the substrate up and down in a desired rangebetween a position where the bottom edge of the substrate is presentabove the liquid surface of the photoresist film removing solution and aposition where the top edge of the substrate is present below the liquidsurface, or by changeing a level of the liquid surface. This makes itpossible to uniformly remove the photoresist film on the whole of thesurface of the substrate.

By applying the ultrasonic vibration to the sealed system, the rate forthe decomposition and the removal can be further increased.

In the method of the present invention and the apparatus used therefor,when the photoresist film removing solution is used in the form of vaporor mist, reduction of molecular weight of the component remained in thephotoresist film may be also accelerated by contacting with the highconcentration of ozone. Then, the photoresist film may be washed awaywith the photoresist film removing solution in the form of mist, andthereby, the rate of the oxidation and the peeling off.

In the apparatus of the present invention, since the processing vesselfor recovering and processing the excess of ozone and/or the photoresistfilm removing solution to discard or reuse after operation may beinstalled, the amount of the starting material used in the process toremove the photoresist film can be also optimized or minimized.

In addition, since the apparatus of the present invention also equipsthe processing vessel which is able to convert the excess of ozoneand/or the photoresist film removing solution to the harmless gas orsolution before the disposal thereof, an adverse effect on theenvironment is not brought about. Also because the apparatus accordingto the present invention is operated in the sealed system, a toxic gasor vapor will never be released to the atmosphere even when thematerials are used in the form of vapor or mist.

What is claimed is:
 1. An apparatus for removing a photoresist film froma substrate by, in a sealed system, placing a substrate having a surfacecovered with a photoresist film in contact with a liquid photoresistfilm removing solution, supplying ozone near a surface of the liquidphotoresist film removing solution, and cycling relative positions ofthe surface of the substrate and the surface of the liquid photoresistfilm removing solution between a first position, H_(max), where a bottomedge of the substrate is above the surface of the liquid photoresistfilm removing solution, a second position, H_(min), where a top edge ofthe substrate is below the surface of the liquid photoresist filmremoving solution, to remove the photoresist film, and back to the firstposition, wherein the apparatus comprises: a reaction vessel for holdinga liquid photoresist film removing solution, an ozone feed tube havingan outlet for injecting ozone into the liquid photoresist film removingsolution in the reaction vessel, a substrate cassette for placing thesubstrate in contact with the surface of the liquid photoresist filmremoving solution in the reaction vessel, a cassette carrier unit formoving the substrate cassette, and a processing tank for recovering andprocessing at least one of the ozone and the liquid photoresist filmremoving solution.
 2. The apparatus for removing a photoresist filmaccording to claim 1, wherein relative positions of the surface of thesubstrate and the surface of the liquid photoresist film removingsolution are cycled between the first, second, and first positionscontinuously, by moving the cassette carrier unit, to remove thephotoresist film.
 3. The apparatus for removing a photoresist filmaccording to claim 1, wherein relative positions of the surface of thesubstrate and the surface of the liquid photoresist film removingsolution are cycled between the first, second, and first positionsintermittently, by moving the cassette carrier unit, to remove thephotoresist film.
 4. The apparatus for removing a photoresist filmaccording to claim 1, wherein the reaction vessel includes anautomatically operated valve for changing a level of the surface of theliquid photoresist film removing solution.
 5. The apparatus for removinga photoresist film according to claim 1, comprising an ultrasoundgenerator.
 6. The apparatus for removing a photoresist film according toclaim 1, wherein the processing tank includes means for at least one ofreusing and discharging at least one of the liquid photoresist filmremoving solution and ozone.